A continuous flow liquids/solids slurry cleaning, recycling and mixing method, apparatus and system used with drilling apparatus in drilling operations for cleaning slurries so that solids and liquids are separated from each other in a continuous process.
Conventional liquids/solids (slurry hereinafter), recycling and mixing systems generally include several components such as a pit pump, a shaker screen, a primary tank, one or more secondary tanks, reservoir tanks and mixing systems. The pit pump is generally provided for delivering a slurry from a drilling rig to the slurry cleaning, recycling and mixing system. The shaker screen is generally provided for performing an initial removal and separation of solid constituents of the slurry. The tank, generally known as the sand trap, is provided for containing the liquid constituent of the slurry after it has passed over the shaker screen.
The tank allows additional solids to settle out of the slurry before passing over a top weir and to additional secondary tanks. The secondary tanks ranging from a single tank for holding partially cleaned mud to multiple tanks serving as reservoirs can also be provided. The secondary tanks are generally used as reservoirs for desander/desilter systems. The multiple tanks generally serve as reservoirs for a variety of other systems used in drilling operations including degassers, desanders, desilters and centrifuges.
Additional tanks can also generally be provided for holding a reservoir of completely cleaned mud slurry that is ready to be reused by a drilling rig and mixed with other materials that are useful in drilling operations. For example, mud slurries used for drilling are generally mixed prior to reuse by adding polymers or Bentonite as may be required by a given drilling operation. Accordingly, the mixing systems are generally provided for initial mixing of the Bentonite and/or the polymers.
However, the related art systems described above have several disadvantages. First, the tanks are typically square and thus as slurries flow through them, there is a wide variation in the flow velocity of the slurry within the tanks. For example, in some areas, the flow velocity of the slurry approaches zero and allows the solids to settle out of suspension in a process known as sedimentation. As sedimentation occurs, the tanks eventually fill with the sedimentary solids and require periodic cleaning. Having to conduct periodic cleaning is disadvantageous because it requires additional labor for cleaning the tanks. Moreover, opening the tanks creates a potential for environmental contamination by the inevitable spilling of the tank""s contents in the local environment. Furthermore, the periodic cleaning operation results in additional cost in making the tanks accessible for cleaning. In order to reduce the sedimentation, several conventional systems have added a mechanical agitator to each tank in an effort to keep the solids in suspension.
Other disadvantages of conventional systems include having a significant volume of slurry in process and thereby rendering a portion of that slurry unavailable as cleaned slurry ready for use in the end operation, e.g., drilling. Moreover, in conventional systems the slurry passes through each various filtering component one at a time.
The present invention is generally directed to a continuous flow slurry cleaning, recycling and mixing system and method used with a drilling apparatus in drilling operations. The invention provides a method, apparatus and system for cleaning slurry so that the solid and liquid constituents of the slurry can be separated in a continuous process. The invention also provides continuous circulation of slurry which keeps solids in suspension and maintains an adequate slurry fluid velocity.
One aspect of the invention provides a method of cleaning liquid/solids slurry having first and second filter stages. The method includes filtering the liquid/solids slurry at the first filter stage; mixing the filtered slurry with liquid ready for use; and re-circulating the mixed liquid through the second filter stage.
An alternative aspect of the invention provides an apparatus for cleaning liquid/solids slurry. The apparatus includes a tank; first and second filter stages, each filter stage having an input portion and output portion, the input portion of the first filter stage being adapted to receive liquid/solids slurry to be cleaned, the first and second filter stages being adapted to filter the liquid/solids slurry; and a manifold in fluid communication with the output portion of the first filter stage and the tank, the manifold being arranged to receive and mix the filtered liquid with liquid ready for use; wherein, the mixed liquid is transferred from the manifold to the second filter stage.
Yet another alternative aspect of the invention provides a system for cleaning liquid/solids slurry. The system includes a drilling apparatus; and an apparatus for cleaning liquid/solids slurry. The apparatus includes a tank; first and second filter stages, each filter stage having an input portion and output portion, the input portion of the first filter stage being adapted to receive liquid/solids slurry to be cleaned, the first and second filter stages being adapted to filter the liquid/solids slurry; and a manifold in fluid communication with the output portion of the first filter stage and the tank, the manifold being arranged to receive and mix the filtered liquid with liquid ready for use; wherein, the mixed liquid is transferred from the manifold to the second filter stage.
Still another alternative aspect of the invention provides a method of cleaning liquid/solids slurry. The method includes transferring the liquid/solids slurry to a first filter stage; separating solids from the slurry and discharging a first filter stage underflow liquid from the first filter stage; routing the first filter stage underflow liquid to a continuous suction manifold assembly; mixing the first filter stage underflow liquid with a second filter stage underflow liquid discharged from the second filter stage and liquid ready for use, resulting in a combined liquid mixture; transferring the combined liquid mixture to the second filter stage; routing the second filter stage underflow liquid from the second filter stage to the continuous suction manifold assembly; and discharging liquid ready for use from the second filter stage into a tank.